You're Asked to Diagnose Something Outside Your Trade: Decision Tree

Why this matters

You are on site for your own work and the customer points at something else. "While you're here, what's wrong with the water heater?" "You do electrical, right, so why does the pool pump keep shutting off?" The pull is to answer, because you want to be helpful and you probably have a hunch. But a diagnosis you put a name to becomes a fact the customer acts on, and if the subject belongs to another trade, a wrong name is one you own without the license or the insurance to back it. This tree keeps you useful without handing you a liability.

Start here: is it an active hazard

Before any judgment below, deal with danger. If the thing they are pointing at is a live hazard (a gas smell, scorched wiring, water pooling under an energized appliance, a leaning water heater, a pool with a bonding fault), the response is not a diagnosis, it is a safety action. Make it safe within your authority: shut off the supply, kill the circuit, keep people back. Tell the customer plainly that it is unsafe and who to call now, the correct trade or the utility. Naming the exact cause comes second, and often it is not yours to name at all.

Once nothing is actively dangerous, decide how far you can go.

The line that matters: observation vs diagnosis

These are two different acts, and only one is safe to give outside your trade.

• An observation is what you can see, hear, smell, or measure, stated as plain fact. "There is water at the base of the tank." "The breaker feeding this is warm to the touch." "The pump hums but the shaft does not turn." You are reporting reality.
• A diagnosis is a named cause with a prescribed fix. "Your gas valve is bad, you need a new one." You are making a claim the customer will spend money on.

Give observations freely. Withhold diagnoses that live in another trade. Most customers only want to know that something is wrong and who to call, and an honest observation plus a referral answers both without exposing you.

If the fundamentals overlap your trade

Sometimes the adjacent fault runs on principles you genuinely hold. An electrician looking at a pool pump understands the motor and the circuit even if pool equipment is not their daily work. There you can reason out loud about the part you actually understand and still stop short of the part you do not.

• State only what you can support with a reading: "This is an electrical supply problem, not the pump itself," if you measured it.
• Do not drift into the specialty. The electrician does not opine on the pool's plumbing, chemistry, or bonding code unless they truly know it.

If it is wholly another trade

If the subject runs on principles you do not hold, keep it to observation and referral.

1. Describe what you see, without a cause attached.
2. Name the trade that owns it.
3. Refer to someone you trust, warm if you can make the call.
4. Do not invent a cause to look knowledgeable. A wrong guess the customer repeats to the next contractor makes you look worse, not better, and can send that contractor down the wrong path.

When the customer pushes for a name

"Just give me your best guess." Hold the line, kindly.

• "I could guess, but a wrong guess costs you money on the wrong part. What I can tell you for certain is what I see right now."
• A guess offered as a favor still becomes the number they act on. Frame the restraint as protecting their wallet, because it is.

Recap: the order to follow

1. Hazard first: make safe, then referral, never a diagnosis in place of a safety action.
2. Separate observation (safe to give anywhere) from diagnosis (keep it inside your trade).
3. Reason only about principles you actually hold, and stop at the specialty line.
4. Wholly another trade: observe, name the trade, refer warm, do not guess a cause.
5. Under pressure, offer certainty about what you see, not a guess about what you cannot.

References

• OSHA general-industry guidance on hazard recognition and making a condition safe before further work.
• State and local licensing scope-of-work rules governing diagnostic opinions in other trades.
• Trade-standard practice on referral and disclosure to customers.
• See related: The Honest Line Between Figuring It Out and Referring It Out; Handing Off to a Specialist You Don't Do.